RNA was the first informational polymer

The emergence of genetic replication coincided with the formation of the first RNA molecules.
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Another polymer preceded RNA

Information transfer and genetic replication existed in molecules before RNA.
Created at: 
2020-04-08
  Updated at: 
2020-04-20
Curator:
Tyler Roche   Subscribe ...

Background

Building Block Selection

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Ribonucleotides can form through selective prebiotic pathways.

eThere is a prebiotically plausible pathway from building blocks to ribonucleotides.

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The phosphate linkage is far from the easiest ionic linkage that could have evolved on the early Earth.

eOrganic acids could have provided a more facile and reversible linkage than phosphate in proto-nucleic acid systems.

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RNA’s components can be selectively “picked” from the pool of possible prebiotic monomers

eRibose can be prebiotically selected from a mix of complicated sugars.

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Noncanonical nucleic acids could have formed more easily than canonical nucleic acids on the early Earth.

eNoncanonical nucleobases react with sugars.

eThere are plausible prebiotic routes to non-sugar nucleic acids.

Polymeric selection

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RNA would have been the preferred molecule for polymerization when compared to potential alternatives.

eNonenzymatic primer extension with activated ribonucleotides is more efficient than the same with activated arabinonucleotides.

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Noncanonical nucleosides provide a more favorable scaffold for oligomerization than canonical nucleosides.

eNoncanonical nucleobases self-assemble into hexad structures.

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It would have been too difficult to transition from an RNA-only world to the RNA-DNA world life uses today.

eNucleic acid chimeras are less stable than the corresponding homopolymers.

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RNA could have been a fully sufficient molecule on the early Earth, with both catalytic and informational functions.

eRNA has catalytic functionality in addition to itso informational functionality.

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RNA’s base pairing abilities are perfect for the initial genetic polymer and needed no other precedent.

eRNA has optimal base-pairing strength for its function.